Fan



June 11, 1935- G. DE BOTHEZAT 2,004,571

FAN

Filed Sept. 8, 1931 3 Sheets-Sheet l AITTORNEYS June 11, 1935. r 6. DEBOTHEZAT FAN Filed Sept. 8, 1931 3 Sheets-Sheet 3 v INVENITOR 62 01"vP630 Iii/{gal BY.

ATT'ORNEY Patented June 11, 1935 FAN Application September 8,1931,Serial No. 561,524 12 Claims. (Cl. 230-123) This invention relates torotary fans and par- The air is drawn inward ticularly to fans fordelivering a 'gas such as air compressed somewhat and delivered by the1min'large quantities and against considerable repeller F into the spacebetween sistance.

The object of the invention is to provide such a ther compressed anddelivered in a c fa of simple compact structure and high efiistream fromthe right or outlet end of.

Fig.1 is'an end view of a. fan unit, portional generally to the anglFig. 2 is a vertical sectional view of the same id under hi h th streammeets t aero. with parts broken away, foil and the square of thevelocity W 1 Figs. 3, 4 and 5 are diagrammaticviews illllS- ever thereare a number of aerofoils trating the blade action of the impellers, i rw on whi h a, tream of velocit Fig. 6 is a sectional view of an impellershowing directed, t th i resistance R, of ach aer the hub and bladestructure,

Figs. 7 and 8 are views similar to Fig. 2 but illustratingmodifications,

9 is amend View of a modified form of the aerofoils; this is half thegeometric sum of paratus, and

I e only s l eroforl s Fig. 10 1s a corresponding side view of the sameand W h n mg 8 a 1 .with parts broken away,

Fig. 11 is an end view of a further modification,

and aerofoil, the so-called down wash in this case being only a localphenomenon afiecting part Fig. 12 1s a side view of the same with partsbroken away of the stream only. But in the case of a row of foils (Fig.4) spreading across the stream, In the embodiment of the invention shownin aero Figs. 1 and 2 a cylindrical housing i0 is provided the whole ofthe stlieam 1s deflected and the spindles i2 upon which are rotatablymounted the mg 9 the aerofofls' The more, aerofqils there 40 tudinalbolts l5 passing through the bushing the greater W111 be Ystreamflefiecfilon P170" Spacers is, giving a very light sturdyStructure to duced by theaerofofls. The air resistance R t housing as awhole A driving Humorv n is of each aerofoil W111 be related to theamount of mounted on top of the housing, carrying th pu1.. deflectionthe stream undergoes so that the releys l8 and ill at the opposite endsof the shaft, 81815811166 R depends not Only p h entering the pulley gdriving the pulley 2g of rotor F and velocity W, but also upon thedischarge velocity the pulley l9 driving the pulley 2| of the rotor F Asabove pointed out, this reslstance by means ofareverse idlercombination, described Will be proportional to the Squa of the 5 andclaimed in my copending application Serial metric mean W of W and W". Ifthe blades of No. 514,505. A separate housing 22 may be prothe disk fanare cut by a coaxial cylinder. and

together at the top ridge member 25. foilsso that the law of airresistance for the fan stream behind the second fan F no rotation of thefinal air blaldes will correspond to that of a row of aerofoi S.

If there are two disk fans coaxial and rotating in opposite directionsso that both are operating in the same slip stream (the stream createdby a rotating blade screw being usually called slipstream), and if asshown in Fig. 5 the aerofoil cross sections represent one blade of eachof the disk fans taken at a distance r from the fan axis and if 9 is theangular velocity of rotation, assumed equal but of opposite sense, forboth fans, then the air stream in passing the fan F will acquire anangular velocity w, and after passing fan F the air may still have anangular velocity (0" (all these assumptions being referred to a distancer from the fan axis).

The impellers F, F may be so formed. and related that the first impellerF will impart to the stream a rotational component which will be reducedto zero by the action of the second impeller F so that w" equals zero,then there is stream, and there will be no rotational losses in thedischarge. The losses are thus confined to the blade losses, impact,friction and the like, and high efficiency will be attained. Accordingto the theorem of moments of momentum, the rotating effect of fan F willbe counteracted by fan F when the torques applied to each of the fansare equal in magnitude but opposite in direction. slip-stream leavingfan F will have no rotation because each fan communicates to the airstream equal opposite rotation momentum, and thus the resulting rotationbehind the second fan F will be zero.

The conditions under which impellers F, F operate are not identical, andthere is, therefore, required a complementary change in thecharacteristics of these impellers in order that they shall have equaltorques under these different conditions. The relative velocity W1-to beused to estimate the air resistance on each blade of fan F-is theresultant of the axial stream velocity 'v and the velocity 1' nrw=r(SB-w) where (0 equals one half (0'. But the relative velocity W2 forthe second fan F is the resultant of 12 It thus follows that themagnignitude of W1 or We W1 but the angle of W2 with the plane ofrotation of fan F is smaller W1 with the plane of rotation of fan F. Nowif the angle of attack of the blades of each fan in relation to W1 andW2 respectively is substantially the same, in order to have the torquesequal, fan F must have a smaller total blade area than fan F or asmaller number of blades if both fans have blades of equal size. Inaddition, since it is desirable to have the angles of attacksubstantially the same, the blade angles 1 of the blades of fan F mustbe larger than angles z of the blades of fan F. Only under theseconditions can the resultant pressure on the blades be equal, thetorques being proportional to these resultant pressures.

Therefore, a set of two coaxial disk fans rotating in oppositedirections in their mutual slip stream will have highest efficiency whenthe slip does not rotate. This condition of no rotation will be realizedwhen the torques applied to the fans F, F are equal in magnitude andopposite in direction, and this equalityof torques can only berealized-for two fans rotating speed-when the first fan has more bladesthan the second, in case of blades of equal width, and the blade anglesof 21 carries the the blades of the first fan F are larger than theblade angles of the blades of the second fan, these blade angles beingtaken with respect to the plane of rotation.

Since as above explained the rotational energy communicated to the airby the first impeller can be fully recovered by the second impeller, itis advantageous to form the blading of the first impeller to impart ahigh rotational component to the stream, thus giving the discharge fromthe first impeller F additional energy. To achieve this, very high bladeangles are used in the first impeller F, generally higher than 45, andthe second impeller F, as explained above, has a smaller blade angle, asa rule smaller than 45. In this way the air drawn in by the firstimpeller F of the pair has imparted to itnot only the full axialvelocity required for the desired delivery, but also a'very high angularvelocity around the axis so that the resultant stream line, particularlyin the outer portions of the flow, may be at an angle as high as 45, asshown by a thread line interposed in the stream. This means greatlyincreased efiiciency for the first impeller calculated on the basis of atotal energy delivered to the discharge. Ordinarily, a large proportionof the energy of this whirling discharge would be turbulence due to thewhirl. With cooperating second impeller F, however, this whirl iseffectively and efficiently recovered so that the final discharge issubstantially axial in direction, and the high whirl of the fiowentering the second impeller enables it to also operate very eflicientlyon the stream as a whole so that the combined effects of the twoimpellers represent increase in efficiency over that attainable by asingle impeller producing the same delivery against the same pressure.

The above conclusions have been'tested and confirmed and highefiiciencies, substantially have been attained, and it is found that thestatic pressure developed by a properly cooperating pair of diskimpellers and the air volume delivered thereby are substantially doublethe pressure and delivery of a single disk impeller of the same diameterand speed. Both the pressure and the volume are doubled.

Consequently, good air deliveries and high attainable at relatively lowspeeds, resulting in the very important characteristic of quietness inoperation. The cooperating series of impellers-thus build up pressurefrom stage to stage while efiiciently and silently passing largequantities of air by impeller-blower action.

In Fig. 6 one form of construction of the impeller is shown built up offour parts. The hub blade 28 by means of the connecting disks 29. Theblades 28 are bent to form flanges fitting between the disks 29 andriveted thereto as indicated at 3|, while the inner portions of thedisks 29 are fastened to the fiange of the hub 21 by the through rivets30.

In the modification shown in Fig. I there are a series of impellers I,II, III and IV receiving the air flow at the left and discharging it atthe right. The impellers I and IV are mounted on one shaft 35 passingthrough a hollow are mounted the impellers II and III. Bearings 31 and38 of stays 39 and 40 support'the shaft. The hollow shaft 36 is eithermounted on the shaft 35 stays 39 and 40 at each end. are driven bypulley 4| lted to the pulley 42 at the left end. of the motor 43, thepulley 44 at the shaft 36 on which so that pulleys 4| and 45 are drivenin opposite ponents. Then the second impeller recovers this 5directions. For small powers a cross belt could rotational energy andfinally delivers the air be used instead of the reversing idlers. Thisunder increased pressure and with the discharge construction providestwo pairs of impellers with substantially axial in direction. themembers of each pairrotating in opposite I claim:

directions. The impellers II and III have the 1. A fan unit consistingof a housing and a l0 l5 velocity imparted to the flow by the impellerI. charging the gas at the opposite end of the series In Fig. 8 amodification is shown providing for with substantially no rotation ofthe discharge six or eight impellers in series. Impellers I, IV, aroundthe axis, and means for driving said im- V and VIII are mounted on oneshaft 50 passing pellers with relatively opposite rotations atsubthrough two hollow shafts 5|, 52 on which are stantially the samespeed the impellers rotating mounted respectively the impeller sets II,III, in opposite directions having their respective 20 VI and VII. Theimpeller set II,-III on hollow blade widths and blade angles and thenumber shaft 5| is driven by the pulley 53 from the moof bladesdifferent as to at least one of these I 25. motor'pulley 55 and thereversing idlers 56. The operating conditions. 5

rotating in opposite directions; This combinapair rotating in oppositedirections with respect to each othe 5 also by central bearing 60 andend bearings 6| ing their respective blade widths and blad and 62. Thehollow shaft Si is journaled in the angles and the number of bladesdiiTerent as to bearing 63, and' hollow shaft 52 in bearing 64, at leastone of these features and so related that from the housing by anydesired form of stay cal under normal operating conditions. members,such as those indicated at B5. 3. A fan unit comprising a pair ofcoaxial disk 40 Instead of reversing by idler pulleys, a reversfanimpellers drawing a supply of gas at one ion so as to give drives inopposite directions at proportionately large, and the following impellerthe opposite ends of the motor. being adapted to substantiallyneutralize said In Figs. 9 and 10 a motor 60' is mounted on'a rotationand deliver the stream substantiallybase 6| supporting th f n h ing theaxially, the impellers rotating in oppositedirec 50 s provided for byreversing gears contained in blades so related that their torqueresistances are the extension housin a he nd f he m substantiallyidentical under normal operating 35 tor 60'. conditions. In Figs. 11 and12 a further modification is 4. A fan unit comprising apair ofcoaxial'disk shown in which the motor 65 carries the imfan impellersdrawinga supply of gas at one Dellers F, F, the motor being mount d by sys end, passing it through the space between the 66' in the casing 61'on base 68'. Reducti n impellers, and discharging it at the oppositeend, 0 g aring is p ovided between e tor a matu e the first impellerhavinglarge angle blades adapt-. and the impell r ha this gearing f heimed to impart a rotation 'of over 25 to its dis-' peller F beingenclosed in the ca While charge stream so that the rotational energy inthe gearing or the impeller is enclosed n the discharge isproportionately large, and the the casing 70'. The entire motor assemblyforms following impeller having relatively fewer blades one unit and thereduct n gearings are e nat angles smallerthan those of the precedingimstructed to drive the impelle in opp direcpeller adapted tosubstantially neutralize said tions. rotation and deliver the streamsubstantially axpair imparts a rotation to its discharge so that 5. Afan unit comprising a pair of coaxial disk the stream lines between theimpellers of each fan impellers drawing a supply of gas at one pair aregenerally helical and with a helix angle end, passing it through thespace between the widths and impellers, and discharging it at theopposite end, the first impeller having blades at angles over 45",adapted to impart a rotation of over 25 to its discharge stream so thatthe rotational energy in the discharge is proportionately large, and thefollowing impeller having blades at angles less than 45 adapted tosubstantially neutralize said rotation and deliver the streamsubstantially axially, the impellers rotating opposite directions havingtheir respective rotary speeds and blade widths and the number of bladesso related that their torque resistances are substantially identicalunder normal operating conditions.

6. A fan unit consisting of one or more pairs of disk impellers inseries, the impellers of each pair rotating in opposite directions withrespect to each other, a housing in, which said impellers are mountedand means for driving said impellers, the first impeller of each pairhaving more blades than the second impeller of the pair,

the impellers rotating in opposite directions having their respectiverotary speeds and blade blade angles so related that their torqueresistances are substantially identical under normal operatingconditions.

'7. A fan unit consisting of one or more pairs of disk impellers inseries, the impellers of each pair rotating in opposite directions withrespect to each other,'a housing in'which said impellers are mounted andmeans for driving said impellers, the first impeller of each pair havingmore blades and larger blade angles than the second impeller of thepair,

speeds and blade widths so related that their torque resistances aresubstantially identical under normal operating conditions.

8. A fan unit consisting of pairs of disk impellers in series, theimpellers of each pair rtating in opposite directions with respect toeach other, a housing in which said impellers are mounted and means fordriving said impellers, the first impeller of each pair having largerblade angles than the second impeller of the pair, the impellersrotating in opposite directions having their respective rotary speedsand blade widths and the number of blades so related that their torqueresistances are substantially identical under normal operatingconditions.

9. A four-stage fan unit comprising two pairs of impellers in series,each pair separated by intervening air spaces of greater axial extentthan the impeller blades, the impellers of each pair having theirindividual impellers rotating in the impellers rotating in oppositedirections having their rotary rotating each opposite directions andmeans for driving all of said impellers from a single motor, theimpellers rotating in opposite directions having their respective rotaryspeeds and blade widths and bladeangles and the number of blades sorelated that their torque resistances are substantially identicalundernormal operating conditions.

10. An eight-stage fan unit comprising four pairs of impellers in serieswith the individual impellers of each pair rotating in oppositedirections, and means for driving all of said impellers from a singlemotor comprising a shaft for the first, fourth, fifth and eighthimpellers and separate shafts for the second and third and sixth andseventh impellers, and a single motor means for driving said firstmentioned shaft in one direction and the remaining shafts in theopposite direction, the impellers rotating in opposite directions havingtheir respective rotary speeds and blade widths and blade angles and thenumber of blades so related that their torque resistances aresubstantially identical under normal operating conditions.

11. A fan unit comprising, housing symmetrical about mounted on saidaxis, rotating each of the two fans constituting a pair in oppositedirections and with speeds having at all times a definitelypredetermined ratio, the blading for the first impeller having highblade angles designed to create a pronounced spiral flow, the secondimpeller having much smaller blade angles, and the blade width and bladearea being designed to give the second impeller substantially the sametorque in reverse direction as the first impeller and to convert thespiral flow into an axial flow at higher pressure than at entry into thepair.

12. A fan unit comprising, in combination, a housing symmetrical aboutits axis, disk fans mounted on said axis, driving means suitable for ofthe two fans constituting a pair in opposite directions and with speedshaving at all times a definitely predetermined ratio, the blading forthe first impeller having high blade angles designed to create apronounced spiral flow, the second impeller havingv much smaller bladeangles and fewer blades, and the blade in combination, a its axis, diskfans width and blade area being designed to give' the second impellersubstantially 'the same torque in reverse direction as the firstimpeller and to convert the spiral flow into an axial flow at higherpressure than at entry into the pair.

GEORGE or: BOTHEZAT.

driving means suitable for

